This invention relates to a reactor for purification of water by fluid filtration. It is designed for chemical purification of water with homogenization of the created floccular suspension and with separation of this suspension by fluid filtration.
For separation of floccular suspensions generated in the course of the treatment and cleaning of water, reactors with fluid filtration using a perfectly floating fluid floccular layer in the separating space are at present the most efficient arrangements. The efficiency of fluid filtration can be thereby substantially increased by homogenizing the floccular suspension prior to its entrance into the space for fluid filtration. The homogenizing is accomplished by a mechanical movement of a homogenizer, which creates in the homogenizing space a suitable turbulence to which the water with the suspension is exposed for a sufficient time interval (about 15 minutes) in order to create conditions for sufficient influencing of the mixture. The size of the homogenizing space must also correspond to the time interval of the homogenizing action; the size of the homogenizing space is comparable with the size of the separating space. The homogenization creates, in the case of fluid filtration, a more homogenous and a more compact layer with better characteristics of sedimentation. It eliminates the dependence of the efficiency of fluid filtration on the season of the year and enables an effective application of polycoagulants, which improve the efficiency of separation.
Due to a number of drawbacks connected with the separate arrangement of the homogenizing space from the arrangement for separation of the suspension, arrangements are used wherein the homogenization and separation spaces are combined in a compact reactor. Two types of reactors of this kind can be mentioned, namely reactors with a vertical homogenizer axis and reactors with a horizontal homogenizer axis. In both cases the homogenizing space is situated substantially centrally in the reactor. In the case of arrangements with a vertical axis of the homogenizer, the homogenizing space usually has the shape of a cylinder or of a frustrum of a cone, and at its bottom part is connected with the bottom of the separating space. The treated water flows through the homogenizing space from top to bottom and its direction of flow turns upwards in the course of its passage into the separating space. Arrangements with a horizontal axis of the homogenizer have a homogenizing space of the shape of a horizontal or lying prism or cylinder and is connected either directly or by means of lateral connecting channels with the bottom of the separating space. In the first case the treated water flows radially through the homogenizing space; in the second case the water flows along the axis of the homogenizing space and in the opposite direction through the connecting channels.
All of these arrangements have different drawbacks. As the maximum turbulence for homogenizing is optimal at the start with subsequent reduction thereof in the course of this process, the shapes of the homogenizing spaces and the directions of flow therein are in actual arrangements not advantageous for an efficient homogenizing in a different way. The most unfavorable conditions in this regard are for homogenizing spaces in the shape of a frustrum of a cone with a flow from the top to the bottom, and for a prism or cylinder with a horizontal axis and a radial direction of flow.
This drawback can be eliminated by dividing the homogenizing space into a number of sections and by using a number of mechanical homogenizers with different moving speeds; this solution, however, is complicated and expensive. Another drawback of these arrangements is the substantial reduction of the efficiency of separation when starting the operation, before a fluid filtration layer is formed in the separating space after the so-called "starting period".
Arrangements with vertical axes and arrangements with horizontal axes of the homogenizer with a longitudinal flow have an additional drawback in their limitation as to variations of the output within the range from 50 to 100 percent. In case variations surpass these limits, operating failures occur due to choking of the connection between the homogenizing space and separating space by sludge from the separating space. Arrangements with a cylindrical homogenizing space with a vertical axis have the additional drawback of a reduction of the separating surface, thus reducing the output for the overall extent of the surface of the arrangement. Finally, small reactors have another drawback; by reason of design arrangements with a vertical axis of the homogenizing space, these reactors have the water inlet leading into the separating space so narrow that there is a danger of choking, requiring solutions with additional arrangements, for instance, the added step of rinsing. Arrangements with a horizontal axis of the homogenizing space have, due to the complexity of their design, higher first costs than do those arrangements with a vertical axis of the homogenizing space.